Cawley et al. 2020 did not realize Mesozoic pycnodonts were derived from extant bonefish

Cawley et al. 2020
brought us an overview of a clade of Mesozoic fish, the Pycnodontiformes (Fig. 1).

From the abstract
“Two other neopterygian clades possessing similar ecological adaptations in both body morphology (†Dapediiformes) and dentition (Ginglymodi) also occurred in Mesozoic seas.”

Short note: Dapediformes includes Dapedium and kin (taxa related to gars, like Lepisosteus in the LRT). Ginglymodi includes Semionotiformes (Semionnotus) and Lepidotidae (Lepidotes and Lepisosteus (= gars)). These taxa nest basal to catfish + placoderms in the LRT. They are Silurian in origin, not related to Pycnodus (Fig. 2) and Albula (Figs. 1, 3) in the LRT.

From the introduction:
“The overarching goal of this study is to evaluate the success but also final demise of pycnodontiform fishes, which represented the major marine actinopterygian elements from the Late Triassic to Palaeogene.”

Figure 1. Color image from Cawley et al. 2020. Albula added. Taxa below the gray line are Semionotiformes unrelated to pycnodontiformes.

Figure 1. Color image from Cawley et al. 2020. Albula added. Taxa below the gray line are Semionotiformes unrelated to pycnodontiformes.

Unfortunately Cawley et al. fails to mention
the extant pycnodontiform, the bonefish, Albula, which nests with the pycnodontiforms, Flagellipinna and Pycnodus (Agassiz 1835), in the large reptile tree (LRT, 1804+ taxa).

Also unfortunately,
Cawley et al. inappropriately includes several members of the Dapediidae and Semionotiformes (Fig. 1). Due to taxon exclusion the authors don’t realize these taxa nest in the other major clade of bony fish, apart from most ray fins, closer to spiny sharks, placoderms and lobefins, far from Pycnodus and Albula.

Cawley et al. reports, 
“Pycnodontiforms represent a well-defined monophyletic group…”

then admits,
“but the intrarelationships of various taxa and groups remain debated.” The LRT tests virtually all other fish clades.

Figure 2. Pycnodus with bones colorized according to tetrapod homologies. Third frame shows maxilla and lacrimal returned to in vivo positions.

Figure 2. Pycnodus with bones colorized according to tetrapod homologies. Third frame shows maxilla and lacrimal returned to in vivo positions.

Wikipedia reports,
Pycnodontiformes is an extinct order of bony fish. The group evolved during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America. The pycnodontiforms were small to middle-sized fish, with laterally-compressed body and almost circular outline. Pycnodontiform fishes lived mostly in shallow-water seas. They had special jaws with round and flattened teeth, well adapted to crush food items. One study links the dentine tubules in pycnodont teeth to comparable structures in the dermal denticles of early Paleozoic fish. Some species lived in rivers and possibly fed on molluscs and crustaceans.”

Figure 1. Albula vulpes skull with highly derived facial bones reidentified here. Note the lateral premaxillary processes and 'floating' cheek bones. Green vertebrae are caudals.

Figure 3. Albula vulpes skull with highly derived facial bones reidentified here. Note the lateral premaxillary processes and ‘floating’ cheek bones. Green vertebrae are caudals.

Pycnodus according to Wikipedia
“The known whole fossils of Pycnodus are around 12 centimetres (5 in) long, and have a superficial resemblance to angelfish or butterflyfish. The animals, as typical of all other pycnodontids, had many knob-like teeth, forming pavements in the jaws with which to break and crush hard food substances, probably mollusks and echinoderms. These teeth are the most common form of fossil.”

According to Wikipedia
Bonefishes live in inshore tropical waters and moves onto shallow mudflats or sand flats to feed with the incoming tide. The bonefish feeds on benthic worms, fry, crustaceans, and mollusks. Ledges, drop-offs, and clean, healthy seagrass beds yield abundant small prey such as crabs and shrimp. It may follow stingrays to catch the small animals they root from the substrate.”

Apparently no one has reported
that pycnodontiformes is an extinct clade within the extant clade Albulidae. Likewise no one has reported that Semionotifomes are not related to Pycnodontiformes. If so, please send the citation so I can promote it here.


References
Agassiz JLR 1835.Recherches sur les Poissons fossiles, 5 volumes. Imprimerie de Petitpierre et Prince, Neuchaatel, 1420 pp.
Bleeker P 1859. xx
Cawley JJ et al. (5 co-authors) 2020.
Rise and fall of Pycnodontiformes: Diversity, competition and extinction of a successful fish clade. Ecology and evolution DOI: 10.1002/ece3.7168

wiki/Pycnodontiformes
wiki/Pycnodus
wiki/Bonefish

Pycnodontiformes Berg 1937
Albulidae Bleeer 1859

 

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